Hoisting ropes typically include one or several load bearing members that are elongated in the longitudinal direction of the rope and each form a structure that continues unbroken throughout the length of the rope. Load bearing members are the members of the rope which are able to bear together the load exerted on the rope in its longitudinal direction. The load, such as a weight suspended by the rope, causes tension on the load bearing member in the longitudinal direction of the rope, which tension can be transmitted by the load bearing member in question all the way from one end of the rope to the other end of the rope. Ropes may further comprise non-bearing components, such as an elastic coating, which cannot transmit tension in the above described way. The coating can be utilized for one or more purposes. For instance, the coating can provide rope with a surface via which the rope can effectively engage frictionally with a drive wheel. The coating can also be used to provide protection for the load bearing members of the rope.
Such hoisting ropes have been suggested where the load bearing members are in the form of elongated fiber-reinforced composite members encased in polymer coating. Composite material of this kind is typically rigid in all directions and thereby also difficult to bend. In hoisting appliances, ropes typically need to be guided by rope wheels, whereby each rope goes through bending during its use. The bending is repeated constantly during the use of the hoisting appliance, whereby internal behavior of the rope during bending is an important factor in service life of the rope. As it is normally desired that the ropes have a maximally long service life, it is not recommendable to guide the rigid ropes around so small-radius rope wheels that a too sharp bending would be caused for the rope in question. Sharp bends might cause local internal stresses on the load bearing member that could be damaging for the load bearing member or at least shorten the service life of the load bearing member in long term use. One or more of the above given aspects of rope behavior in bending, among several other aspects, need to be taken into account when designing the layout of the elevator and selecting the size of the rope wheels. A drawback has been that this limits the freedom of design of the elevator. In general, the thicker the cross section of the load bearing members are, the larger the bending radius should be. Thus, the designer has been limited to a certain size range of a rope wheel when selecting a rope wheel for a given load bearing cross section.